Those are pretty cool. I especially like the one made from multiple binder clips with the laser pointer aiming system.

When I was (much) younger, I was a paperboy. Along with jogging my route before school, one of the perks was rubber bands. We would get big old bags of them and a bunch of us would have all out rubber band wars in my mother's basement. Once, I made the most terrifying rubber band weapon ever. I took four rubber bands (I think it was four), chained them together, then looped each end over the legs of an upside down stool. Repeat that about ten times, until you have a thick cord of rubber bands. Now make a projectile "taco" out of an entire sheet of paper. It left bruises through a field jacket.

We always wore protective gear. We'd raid one of the old wardrobes in the basement for some old field jackets (WWII or Korea, probably) and stuff. Goggles came from the workshop room in the back. Still, the super rubber band railgun was outlawed, because its destructive power was judged to be too much. This is coming from kids who would roll M80's in glue, then roll them in BBs and use them as grenades when we had BB gun wars.